1. Field of the Invention
The invention relates to computerized wordprocessing technology and specifically, to a process and apparatus carried out on a digital computer for creating and editing mathematical equations in printed documents.
"Wordprocessing" involves the use of a digital computer to manipulate printed characters in creating and editing documents. Such documents can be displayed electronically on a computer display screen or printed on hardcopy. This patent application was created using a wordprocessing program ("wordprocessor"). Manipulation of data in the form of printed characters is, indeed, a fundamental tool for human interaction with computers. Input devices such as keyboards provide the mechanism for feeding information to the computer, while output devices, such as video display terminals and printers, provide the mechanisms for viewing the results. Wordprocessors are a fundamental and vital tool of modern business.
Wordprocessors range in functionality from simple "text editors," which do no more than reproduce on the display screen the user's keyboard input, to sophisticated "desktop publishers," which enable the user to create, display, and print sophisticated, publication quality documents. An "equation editor" is a method implemented in software that is used to create and edit mathematical equations and which may be a component of a wordprocessor. Mathematicians, economists, businesspersons, and others who frequently utilize mathematical equations often need to incorporate those equations into printed documents such as reports, articles, and other papers. Incorporating complex mathematical equations into standard textual documents for printing has long been a difficult or even impossible undertaking. Because equations contain many non-standard characters and because those characters are often formatted in a complex manner, they are far more difficult to create and print than standard text.
The ability to create and manipulate equations in documents with an equation editor is partially constrained by the keyboard. Standard computer keyboards contain a character set including the letters "a" through "z", numbers "0" through "9", various commonly used characters such as commas, periods, semicolons, and apostrophes, cursor control keys such as "Page Up", "Page Down", and arrow keys, and ten or twelve special function keys. Standard computer keyboards do not contain many unique characters or symbols frequently used in mathematical equations. Therefore, unlike ordinary text, equations cannot be typed directly into documents using only keyboard characters. For example, while a simple equation such as can be created directly from keyboard characters, a more complex equation such as ##EQU1## cannot be created directly from keyboard characters. Thus, the incorporation of equations into documents created with a wordprocessor requires the use of at least two components: (1) a form of textual description of equations and (2) a "formatter" to translate the textual description into the actual printed form of the equation. For example, even a simple equation such as ##EQU2## cannot be typed directly from the keyboard and therefore must be created using a textual description such as "a OVER b" which can be translated and printed in its equation form. An equation such as ##EQU3## can be created using a textual description such as "FUNC f'(x)=lim--(h.fwdarw.0) {(FUNC f(x+h)-FUNC f(x)}OVER h}".
A sophisticated equation editor also automatically formats equations, performing such tasks as automatic sizing of equation elements such as the root sign or the horizontal separator for division, and the vertical extension of "delimiters" (growing parentheses, brackets) around the sub-equations they enclose. For example, in the equations ##EQU4## the equation editor adjusts the size of the square root sign and the parentheses to fit the equation inside. By automatically performing these awkward and time-consuming tasks, the equation editor frees the user to perform other less tedious tasks.
2. Brief Description of Prior Art
Prior art equation editors, such as TeX, Microsoft Word for the Apple MacIntosh computer and for the Microsoft Windows environment, Lotus Manuscript and EQN for Unix systems all include a method for describing equations textually and an equation formatter for translating the textual description into the printed form of the equation. However, prior art equation editors provide neither an editing methodology which allows the efficiency and flexibility of the present invention in creating textual descriptions of equations nor a window in the same display interface to display the final printed form of the equation at the same time as its textual description is being edited. The present invention uniquely combines multiple equation editing components into a single user interface, including an editing window for manipulating the textual description of an equation, a display window for viewing the printed form of the equation, and a palette window for selecting characters and commands used in describing the equation.